Disazo Dyes And Their Use in Ink-Jet Printing

ABSTRACT

A compound of Formula ( 1 ) or a salt thereof: 
     
       
         
         
             
             
         
       
         
         
           
             wherein: 
             X is N or C(CN);
           Z is optionally substituted naphthyl;   Ar is an aryl group carrying at least one substituent selected from the group consisting of an acetyl group, an acetate ester group, an amide group, a sulfonamide group, a sulfoxide group, a sulfone group, a phosphonate group, a nitrile group, an isonitrile group, a quaternary amine, a carbonyl group (other than a carboxylic acid), a polyhaloalkyl group or a halogen atom; and   Ar may optionally be substituted with one or more further substituents.   
         
           
         
       
    
     Also compositions, inks, printing processes, printed material and ink-jet cartridges.

This invention relates to compounds, compositions and inks, to printingprocesses, to printed materials and to ink-jet printer cartridges.

Ink-jet printing is a non-impact printing technique in which droplets ofink are ejected through a fine nozzle onto a substrate without bringingthe nozzle into contact with the substrate. The set of inks used in thistechnique typically comprise yellow, magenta, cyan and black inks.

With the advent of high-resolution digital cameras and ink-jet printersit is becoming increasingly common for consumers to print photographsusing an ink-jet printer.

While ink-jet printers have many advantages over other forms of printingand image development there are still technical challenges to beaddressed. For example, there are the contradictory requirements ofproviding ink colorants that are soluble in the ink medium and yetdisplay excellent wet-fastness (i.e. prints do not run or smudge whenexposed to water). The inks also need to dry quickly to avoid sheetssticking together after they have been printed, but they should notcrust over the tiny nozzles used in the printer. Storage stability isalso important to avoid particle formation that could block theprint-head nozzles especially since consumers can keep an ink-jet inkcartridge for several months. Furthermore, and especially important withphotographic quality reproductions, the resultant images should not faderapidly on exposure to light or atmospheric oxidising gases such asozone. It is also desirable that the shade and chroma of the colorantare within a narrow tolerance so that an image may be optimallyreproduced.

Thus, developing new colorants for ink-jet printing presents a uniquechallenge in balancing all these conflicting and demanding properties.

The present invention aims to provide colorants especially suited foruse in ink jet printing inks which are improved in respect of one ormore of the above properties.

According to a first aspect of the present invention there is provided acompound of Formula (1) or a salt thereof:

wherein:

-   -   X is N or C(CN);    -   Z is optionally substituted alkyl, optionally substituted aryl        or optionally substituted heterocyclyl;    -   Ar is an aryl group carrying at least one substituent selected        from the group consisting of an acetyl group, an acetate ester        group, an amide group, a sulfonamide group, a sulfoxide group, a        sulfone group, a phosphonate group, a nitrile group, an        isonitrile group, a quaternary amine, a carbonyl group (other        than a carboxylic acid), a polyhaloalkyl group or a halogen        atom; and    -   Ar may optionally be substituted with one or more further        substituents.

Z

Preferably Z is optionally substituted C₁₋₁₂-alkyl (especiallyoptionally substituted C₁₋₄-alkyl), optionally substituted phenyl oroptionally substituted naphthyl. It is particularly preferred that Z isoptionally substituted naphthyl.

We have found that Compounds of Formula (1) and salts thereof wherein Zis optionally substituted naphthyl tend to have even better overallproperties for ink jet printing.

In particular we have found these (z=naphthyl) compounds tend to provideprints having even better light and/or ozone fastness. Whilst notwishing to be limited by theory we speculate that the combination of:

-   -   (i) the at least one (compulsory) substituent selected from        acetyl group, an acetate ester group, an amide group, a        sulfonamide group, a sulfoxide group, a sulfone group, a        phosphonate group, a nitrile group, an isonitrile group, a        quaternary amine, a carbonyl group (other than a carboxylic        acid), a polyhaloalkyl group or a halogen atom on the Ar group;        and    -   (ii) the naphthyl group for Z;    -   provides particularly good properties including light fastness.    -   When Z is optionally substituted naphthyl the naphthyl is        preferably attached in the 2-position.    -   Preferably, Z is an unsubstituted naphthyl group.        Optional substituents for Z

Optional substituents which may be present on Z are preferably selectedfrom:

-   -   optionally substituted alkoxy (preferably C₁₋₄-alkoxy),    -   optionally substituted aryl (preferably phenyl),    -   optionally substituted aryloxy (preferably phenoxy),    -   optionally substituted heterocyclyl (preferably heteroaryl),        preferred examples of which include 5- and 6-membered rings        contain 1 or 2 hetero atoms selected from N, S and P;    -   polyalkylene oxide (preferably polyethylene oxide or        polypropylene oxide), phosphato (especially phosphoric acid or        phosphonic acid), nitro, sulfo (especially sulfonic acid),        cyano, halo, ureido, hydroxy, ester (including sulfate and        phosphate esters and especially carboxyester), sulfone,        —NR^(a)R^(b), —COR^(a), —CONR^(a)R^(b), —NHCOR^(a), and        —SO₂NR^(a)R^(b), wherein R^(a) and R^(b) are each independently        H, optionally substituted alkyl (especially C₁₋₄-alkyl),        optionally substituted aryl or optionally substituted        heteroaryl.

When Z is aryl, aryloxy or heterocyclyl it may also carry optionallysubstituted alkyl (especially C₁₋₄-alkyl) substituents.

When present the optional substituents on the optionally substitutedalkoxy, aryl, aryloxy, heterocyclyl and alkyl groups (as motioned abovein respect of the Z group) may be selected from halo, amino, nitro,cyan(O) hydroxy, sulfonic acid, carboxylic acid and phosphonic acidgroups.

When present, halo is preferably Cl, Br or F.

Preferred optional substituents for Z are water solubilising groupsparticularly carboxy (especially carboxylic acid), sulfo (especiallysulfonic acid) and phosphato (especially phosphonic acid) and moreespecially carboxy and sulfo.

Ar

Preferably Ar is phenyl or more preferably naphthyl. (The substituentspossible being as hereinbefore described).

More preferably Ar is naphthyl carrying at least one of the compulsorysubstituents and optionally at least one further substituent.

When Ar is naphthyl it is preferably attached in the 2-position.

Compulsory Substituents on Ar

It will be appreciated that the Ar group must compulsorily carry atleast one substituent selected from the group consisting of an acetylgroup, an acetate ester group, an amide group, a sulfonamide group, asulfoxide group, a sulfone group, a phosphonate group, a nitrile group,an isonitrile group, a quaternary amine, a carbonyl group (other than acarboxylic acid), a polyhaloalkyl group or a halogen atom. We have foundthat these electron withdrawing groups tend to improve the light and/orozone fastness of the compounds of Formula (1) and salts thereof.

If present the polyhalo alkyl group is preferably —CF₃.

If present the halogen atom is preferably Cl, Br or F.

Preferably, at least one of the compulsory substituent groups on Ar isselected from nitrile (—CN), sulfone and sulfonamide substituents.

Preferably, at least one of the compulsory substituents on Ar isselected from —CN, —SO₂R¹ and especially —SO₂NR²R³ substituents whereinR¹ is optionally substituted alkyl, optionally substituted aryl oroptionally substituted heterocyclyl and R² and R³ are independently H,optionally substituted alkyl, optionally substituted aryl or optionallysubstituted heterocyclyl

Preferably, R¹ is optionally substituted C₁₋₄-alkyl, optionallysubstituted phenyl or optionally substituted naphthyl.

It is particularly preferred that R¹ is: C₁₋₄-alkyl carrying one or morewater solubilising groups selected from the group consisting of carboxy(especially carboxylic acid), sulfo (especially sulfonic acid) andphosphato (especially phosphonic acid) and especially carboxy and sulfo;optionally substituted phenyl carrying one or more water solubilisinggroups selected from the group consisting of carboxy (especiallycarboxylic acid), sulfo (especially sulfonic acid) and phosphato(especially phosphonic acid) and especially carboxy and sulfo; oroptionally substituted naphthyl carrying one or more water solubilisinggroups selected from the group consisting of carboxy (especiallycarboxylic acid), sulfo (especially sulfonic acid) and phosphato(especially phosphonic acid) and especially carboxy and sulfo.

R² and R³ are preferably selected from the group consisting of H; anaryl group carrying one or more water solubilising groups selected fromthe group consisting of carboxy (especially carboxylic acid), sulfo(especially sulfonic acid) and phosphato (especially phosphonic acid)and especially carboxy and sulfo; and C₁₋₄-alkyl carrying one or morewater solubilising groups selected from the group consisting of carboxy(especially carboxylic acid), sulfo (especially sulfonic acid) andphosphato (especially phosphonic acid) and especially carboxy and sulfo.

More especially, it is preferred that one of R² and R³ is H and theother is:

-   -   i) phenyl carrying at least one group selected from carboxy and        sulfo groups; or    -   ii) naphthyl carrying at least one group selected from carboxy        and sulfo groups.

Even more preferably, at least one of the compulsory substituent on Aris a naphthyl sulphonamide of the formula —SO₂NR²R³ wherein R² isnapthyl which is substituted with from 1 to 3 groups selected fromsulfonic acid, carboxylic acid and phosphonic acid groups and R³ is H.Preferably Ar carries from 1 to 3 and especially 1 or 2 of the abovementioned naphthyl sulfonamide substituents.

It is particularly preferred that the naphthyl sulphonamide is of theFormulae:

Optional Further Substituents on Ar

It will be appreciated that the further substituents are other thanthose mentioned as compulsory substituents.

Optionally, Ar is not substituted with any nitro groups.

When present the optional further substituent on Ar is preferablyselected from:

optionally substituted alkyl;

optionally substituted alkoxy,

optionally substituted aryl,

optionally substituted aryloxy,

optionally substituted heterocyclyl,

polyalkylene oxide, sulfonic acid, carboxylic acid, hydroxy and nitrogroups.

When present the optional substituents on the optionally furthersubstituted alkyl, alkoxy, aryl, aryloxy and heterocyclyl (as motionedabove in respect of the Ar group) may be selected from halo, amino,nitro, cyano, hydroxy, sulfonic acid, carboxylic acid and phosphonicacid groups.

Preferably, Ar is not substituted with electron donating groups such asalkyl, aryl or heterocyclyl groups. Preferably, Ar only carries groupsselected from the compulsory list of substituents which are electronwithdrawing.

Preferably, from 1 to 3 water solubilising groups are directly orindirectly attached to Ar. The preferred water solubilising groups arecarboxy (especially carboxylic acid), phosphato (especially phosphonicacid) and more preferably sulfo (especially sulfonic acid).

General Preferences for Substituents

When Z, R¹, R² and R³ are optionally substituted alkyl they may, belinear, branched or cyclic alkyl groups. When R¹, R² and R³ areoptionally substituted alkyl preferably they are optionally substitutedC₁₋₁₂ alkyl, and more preferably optionally substituted C₁₋₄ alkyl.

When R¹, R² and R³ are optionally substituted aryl they are preferablyoptionally substituted phenyl or naphthyl.

When Z, R¹, R² and R³ are optionally substituted heterocyclyl they arepreferably a 5- or 6-membered ring containing N and optionally 1 or moreother heteroatoms.

Fibre Reactive Croups

The compounds of Formula (1) or a salts thereof are also preferably freefrom fibre reactive groups. The term fibre reactive group is well knownin the art and is described for example in EP 0356014 A1. Fibre reactivegroups are capable, under suitable conditions, of reacting with thehydroxyl groups present in cellulosic fibres or with the amino groupspresent in natural fibres to form a covalent linkage between the fibreand the dye. As examples of fibre reactive groups excluded from thecompounds of Formula (1) there may be mentioned aliphatic sulfonylgroups which contain a sulfate ester group in beta-position to thesulfur atom, e.g. beta-sulfato-ethylsulfonyl groups, alpha,beta-unsaturated acyl radicals of aliphatic carboxylic acids, forexample acrylic acid, alpha-chloro-acrylic acid, alpha-bromoacrylicacid, propiolic acid, maleic acid and mono- and dichloro maleic; alsothe acyl radicals of acids which contain a substituent which reacts withcellulose in the presence of an alkali, e.g. the radical of ahalogenated aliphatic acid such as chloroacetic acid, beta-chloro andbeta-bromopropionic acids and alpha, beta-dichloro- and dibromopropionicacids or radicals of vinylsulfonyl- or beta-chloroethylsulfonyl- orbeta-sulfatoethyl-sulfonyl-endo-methylene cyclohexane carboxylic acids.Other examples of cellulose reactive groups are tetrafluorocyclobutylcarbonyl, trifluoro-cyclobutenyl carbonyl, tetrafluorocyclobutylethenylcarbonyl, trifluoro-cyclobutenylethenyl carbonyl; activated halogenated1,3-dicyanobenzene radicals; and heterocyclic radicals which contain 1,2 or 3 nitrogen atoms in the heterocyclic ring and at least onecellulose reactive substituent on a carbon atom of the ring, for examplea triazinyl halide.

It will be appreciated that all of above mentioned preferredsubstituents are not fibre reactive groups.

Salts

When acid or basic groups (particularly acid groups) are present in thecompounds of Formula (1) they are preferably in the form of a salt.Thus, all Formulae shown herein include the compounds in salt form.

Preferred salts are alkali metal salts, especially lithium, sodium andpotassium, ammonium and substituted ammonium salts (including quaternaryamines such as ((CH₃)₄N⁺) and mixtures thereof. Especially preferred aresalts with sodium, lithium, ammonia and volatile amines, more especiallylithium and sodium salts. Compounds of Formula (1) where lithium is themajor salt form are especially preferred. Preferably, the compounds ofFormula (1) is in the form of a lithium salt.

Compounds of Formula (1) may be converted into a salt using knowntechniques.

The compounds of Formula (1) and salts thereof may exist in tautomericforms other than those shown in this specification. These tautomers areincluded within the scope of the present invention and its claims.

Preferred Compounds of Formula (1)

Preferred compounds of Formula (1) and salts thereof are of the Formulae(2) to (4) and salts thereof:

The above compounds of Formulae (2) to (4) have been found to display,among other things, especially good light fastness.

Preferably, the compounds of Formulae (2) to (4) or a salt thereof arein the form of the lithium salt.

Other compounds of Formula (1) or salts thereof include those ofFormulae (5) to (10) and salts thereof:

Synthesis

The compounds of Formula (1) and salts thereof may be prepared by anymethod known in the art, and particularly by processes such as thosedescribed in U.S. Pat. No. 7,192,475 which is incorporated herein byreference.

The compounds of Formula (1) or salts thereof described herein can besynthesised by methods known in the art. For example, an aryl amine maybe diazotised under aqueous conditions with sodium nitrite andhydrochloric acid. The diazotised aryl amine may then be added to asolution or suspension of a cyano substituted thiophene amine or athiazole amine. Sometimes, a miscible organic solvent such as methanolor N-methyl-2-pyrrolidone can be used as a cosolvent in conjunction withwater. The resulting monoazo compound, once isolated, can be reactedwith a pyridine-based coupler in a manner that ensures diazotisation andcoupling occur in situ. For this coupling step it may be advantageous touse for example isoamyl nitrite.

Alternatively, a step-wise synthetic method can be used, for example themonoazo compound may be diazotised prior to the coupling reaction.

One suitable synthetic method is described schematically as indicatedbelow:

wherein Ar, X and Z are as hereinbefore defined.

The compounds of Formula (1) and salt thereof are valuable colorants foruse in the preparation of ink-jet printing, especially black, inks. Theybenefit from a good balance of solubility, storage stability andfastness to water, ozone and light. In particular they display excellentlight fastness.

Compositions and Inks

According to a second aspect of the present invention there is provideda composition comprising a compound of Formula (1) or a salt thereofaccording to the first aspect of the invention and a liquid medium.

Preferred compositions according to the second aspect of the inventioncomprise:

-   -   (a) from 0.01 to 30 parts of a compound of Formula (1) or a salt        thereof according to the first aspect of the present invention;        and    -   (b) from 70 to 99.99 parts of a liquid medium;        wherein all parts are by weight.

Preferably, the number of parts of (a)+(b)=100.

The number of parts of component (a) is preferably from 0.1 to 20, morepreferably from 0.5 to 15, and especially from 1 to 5 parts. The numberof parts of component (b) is preferably from 80 to 99.9, more preferablyfrom 85 to 99.5 and especially from 95 to 99 parts.

Preferably component (a) is completely dissolved in component (b).Preferably component (a) has a solubility in component (b) at 20° C. ofat least 1% by weight, more preferably at least 2%, especially at least5% and most especially at least 10% by weight. This allows thepreparation of liquid dye concentrates that may be used to prepare moredilute inks and reduces the chance of the dye precipitating ifevaporation of the liquid medium occurs during storage. Preferably, theliquid medium for establishing the required solubility is water.

Thus, the present invention also provides a composition (preferably anink) where component (a) is present in an amount of 2.5 to 7 parts, morepreferably 2.5 to 5 parts (a high concentration ink) or component (a) ispresent in an amount of 0.5 to 2.4 parts, more preferably 0.5 to 1.5parts (a low concentration ink).

Preferred liquid media include water, a mixture of water and organicsolvent and organic solvent free from water. Preferably, the liquidmedium comprises a mixture of water and organic solvent or organicsolvent free from water.

When the liquid medium (b) comprises a mixture of water and organicsolvent, the weight ratio of water to organic solvent is preferably from99:1 to 1:99, more preferably from 99:1 to 50:50, especially from 99:1to 70:30 and most especially from 95:5 to 80:20.

It is preferred that the organic solvent present in the mixture of waterand organic solvent is a water-miscible organic solvent or a mixture ofsuch solvents. Preferred water-miscible organic solvents includeC₁₋₆-alkanols, preferably methanol, ethanol, n-propanol, isopropanol,n-butanol, sec-butanol, tert-butanol, n-pentanol, cyclopentanol andcyclohexanol; linear amides, preferably dimethylformamide ordimethylacetamide; ketones and ketone-alcohols, preferably acetone,methyl ether ketone, cyclohexanone and diacetone alcohol; water-miscibleethers, preferably tetrahydrofuran and dioxane; diols, preferably diolshaving from 2 to 12 carbon atoms, for example ethylene glycol, propyleneglycol, butylene glycol, pentylene glycol, hexylene glycol andthiodiglycol and oligo- and poly-alkyleneglycols, preferably diethyleneglycol, triethylene glycol, polyethylene glycol and polypropyleneglycol; triols, preferably glycerol and 1,2,6-hexanetriol;mono-C₁₋₄-alkyl ethers of diols, preferably mono-C₁₋₄-alkyl ethers ofdiols having 2 to 12 carbon atoms, especially 2-methoxyethanol,2-(2-methoxyethoxy)ethanol, 2-(2-ethoxyethoxy)-ethanol,2-[2-(2-methoxyethoxy)ethoxy]ethanol,2-[2-(2-ethoxyethoxy)-ethoxy]-ethanol and ethyleneglycol monoallylether;cyclic amides, preferably 2-pyrrolidone, N-methyl-2-pyrrolidone,N-ethyl-2-pyrrolidone, caprolactam and 1,3-dimethylimidazolidone; cyclicesters, preferably caprolactone; sulfoxides, preferably dimethylsulfoxide; and sulfones, preferably sulfolane. Preferably the liquidmedium comprises water and 2 or more, especially from 2 to 8,water-miscible organic solvents.

Especially preferred water-miscible organic solvents are cyclic amides,especially 2-pyrrolidone, N-methyl-pyrrolidone and N-ethyl-pyrrolidone;diols, especially 1,5-pentane diol, ethyleneglycol, thiodiglycol,diethyleneglycol and triethyleneglycol; and mono-C₁₋₄-alkyl andC₁₋₄-alkyl ethers of diols, more preferably mono-C₁₋₄-alkyl ethers ofdiols having 2 to 12 carbon atoms.

When the liquid medium comprises organic solvent free from water, (i.e.less than 1% water by weight) the solvent preferably has a boiling pointof from 30 to 200° C., more preferably of from 40 to 150° C., especiallyfrom 50 to 125° C. The organic solvent may be water-immiscible,water-miscible or a mixture of such solvents. Preferred water-miscibleorganic solvents are any of the hereinbefore-described water-miscibleorganic solvents and mixtures thereof. Preferred water-immisciblesolvents include, for example, aliphatic hydrocarbons; esters,preferably ethyl acetate; chlorinated hydrocarbons, preferably CH₂Cl₂;and ethers, preferably diethyl ether; and mixtures thereof.

When the liquid medium comprises a water-immiscible organic solvent,preferably a polar solvent is included because this enhances solubilityof the mixture of dyes in the liquid medium. Examples of polar solventsinclude C₁₋₄-alcohols and ketones.

In view of the foregoing preferences it is especially preferred thatwhere the liquid medium is organic solvent free from water it comprisesa ketone (especially methyl ethyl ketone) and/or an alcohol (especiallya C₁₋₄-alkanol, more especially ethanol or propanol).

The organic solvent free from water may be a single organic solvent or amixture of two or more organic solvents. It is preferred that when theliquid medium is organic solvent free from water it is a mixture of 2 to5 different organic solvents. This allows a liquid medium to be selectedthat gives good control over the drying characteristics and storagestability of the ink.

Liquid media comprising organic solvent free from water are particularlyuseful where fast drying times are required and particularly whenprinting onto hydrophobic and non-absorbent substrates, for exampleplastics, metal and glass.

The liquid media may of course contain additional components suitablefor use in ink-jet printing inks, for example viscosity and surfacetension modifiers, corrosion inhibitors, biocides, kogation reducingadditives and surfactants which may be ionic or non-ionic.

Colour Blends

The compositions and inks described above may contain one compound ofFormula (1) or a salt thereof or a mixture of two or more compounds ofFormula (1) or salts thereof.

Optionally, further colorant(s) not of Formula (1) or a salt thereof maybe added to the ink to modify the shade and performance properties. Theymay also be added to adjust the cost:performance ratio.

The further colorant(s) may be of any colour (including cyan, magenta,yellow and especially black). Preferably, the further colorant arethemselves suitable for ink jet printing inks. Further colorants may beselected from those listed in the Colour Index, and salts thereof, andthose commercially available specifically for ink-jet printing. Thefurther colorants may be pigments but more preferably they are dyes andespecially water soluble dyes.

Preferably, the further colorants are selected from those disclosed inU.S. Pat. No. 7,491,266, and U.S. Pat. No. 7,533,978, the examples ofwhich are incorporated herein by reference.

Suitable further black colorants include C.I. Food Black 2, C.I. DirectBlack 19, C.I. Reactive Black 31, PRO-JET™ Fast Black 2, C.I. DirectBlack 195; C.I. Direct Black 168; and black dyes described in patents byLexmark (e.g. EP 0539178 A2, Example 1, 2, 3, 4 and 5) and OrientChemicals (e.g. EP 0347803 A2, pages 5-6, azo dyes 3, 4, 5, 6, 7, 8, 12,13, 14, 15 and 16)

Suitable further magenta colorants include PRO-JET™ Fast Magenta 2.

Suitable further yellow colorants include C.I. Direct Yellow 142; C.I.Direct Yellow 132; C.I. Direct Yellow 86; C.I. Direct Yellow 85; C.I.Direct Yellow 173; and C.I. Acid Yellow 23.

Suitable further cyan colorants include phthalocyanine colorants, e.g.Direct Blue 199 and Acid Blue 99.

It will be appreciated that the compositions and inks described abovemay be used as the black ink in a colour printing ink set. Suitablecolorants for the magenta, yellow and cyan inks in the set are wellknown in the arts and can be chosen readily from any of those disclosedin the art or commercially available. The further magenta, yellow andcyan colorants described above may be used to prepared the yellow,magenta and cyan inks in the ink set.

It is preferred that the composition according to the second aspect ofthe present invention is an ink suitable for use in an ink-jet printer.Such a composition may also be referred to herein simply as an “ink jetprinter ink”. Ink suitable for use in an ink-jet printer is ink which ispreferably able to repeatedly fire through an ink-jet printing headwithout causing blockage of the fine nozzles. To do this the ink ispreferably substantially free of particles of a size of greater than 1micron in diameter, stable (i.e. does not precipitate on storage and hasa viscosity which allows for good droplet formation at the print head.For thermal ink jet printer inks it is also preferred that thecomposition is substantially free from metal corrosive components suchas chloride ions.

Ink suitable for use in an ink-jet printer preferably has a viscosity ofless than 30cP, more preferably less than 20 cP, especially less than 10cP and most especially less than 5 cP at 25° C. 1cPs equals 1 mPa·s.

Ink suitable for use in an ink-jet printer preferably contains less than500 ppm, more preferably less than 250 ppm, especially less than 100ppm, more especially less than 10 ppm in total of divalent and trivalentmetal ions (other than any divalent and trivalent metal ions bound to acompound of Formula (1) or any other colorant or additive incorporatedin the ink).

Preferably ink suitable for use in an ink-jet printer has been filteredthrough a filter having a mean pore size below 10 μm, more preferablybelow 3 μm, especially below 2 μm, more especially below 1 μm. Thisfiltration removes particulate matter that could otherwise block thefine nozzles found in many ink-jet printers.

Preferably, ink suitable for use in an ink-jet printer contains lessthan 500 ppm, more preferably less than 250 ppm, especially less than100 ppm, more especially less than 10 ppm in total of halide ions.

Printing Process

According to a third aspect of the present invention there is provided aprocess for forming an image on a substrate comprising ink jet printinga composition according to the second aspect of the present inventionwhich is suitable for use in an ink-jet printer (an ink jet printer ink)to the substrate.

The ink-jet printer preferably applies the ink to the substrate in theform of droplets that are ejected through a small orifice onto thesubstrate. Preferred ink-jet printers are piezoelectric ink-jet printersand thermal ink-jet printers. In thermal ink-jet printers, programmedpulses of heat are applied to the ink in a reservoir by means of aresistor adjacent to the orifice, thereby causing the ink to be ejectedfrom the orifice in the form of small droplets directed towards thesubstrate during relative movement between the substrate and theorifice. In piezoelectric ink-jet printers the oscillation of a smallcrystal causes ejection of the ink from the orifice. Alternately, theink can be ejected by an electromechanical actuator connected to amoveable paddle or plunger, for example as described in InternationalPatent Application WO00/48938 and International Patent ApplicationWO00/55089.

The substrate is preferably paper, plastic, a textile, metal or glass,more preferably paper, an overhead projector slide or a textilematerial, especially paper.

Preferred papers are plain or treated papers which may have an acid,alkaline or neutral character. Photographic quality papers areespecially preferred. In some embodiments the paper may have an ink jetreceptor coating which may be porous or swellable.

Printed Material (Substrate)

According to a fourth aspect of the present invention there is provideda material (substrate) printed with a compound or a salt thereofaccording to the first aspect of the present invention, a compositionaccording to the second aspect of the invention or by means of a processaccording to the third aspect of the invention.

The material used is preferably paper, plastic, a textile, metal orglass, more preferably paper, an overhead projector slide or a textilematerial, especially paper more especially plain, coated or treatedpapers

It is especially preferred that the printed material of the fourthaspect of the invention is a print on a photographic quality paperprinted using a process according to the third aspect of the presentinvention.

According to a fifth aspect of the present invention there is providedan ink-jet printer cartridge comprising a chamber and a compositionaccording to the second aspect of the present invention which issuitable for use in an ink-jet printer, wherein the composition is inthe chamber.

The invention is further illustrated by the following Examples in whichall parts and percentages are by weight unless otherwise stated.

EXAMPLE 1 Preparation of the Lithium Salt of

Stage 1a Preparation of

2-Naphthylamine-6-sulfonic acid (Bronner acid) (supplied by TCI, 111.5g; 0.5 mol) was stirred in water at pH 9.5 to form a solution. Aceticanhydride (76.0 g: 0.075 mol) was then added dropwise to the solution ata temperature under 25° C. to form a reaction mixture. The reactionmixture was stirred overnight at room temperature. The product wasprecipitated by the addition of 30% aqueous sodium chloride, collectedby filtration and washed with 25% aqueous sodium chloride solution. Theresultant precipitate was stirred with acetone, collected by filtrationand the treatment was repeated. The resulting solid was dried in an ovento give an off white solid (144.5 g).

Stage 1b Preparation of

The product of stage 1a (78.4 g: 0.20 mol) was added to stirredchlorosulfonic acid at a temperature of less than 20° C. over 1 hour andthen stirred at room temperature overnight. The resulting solution wasdrowned into ice/water causing the product to precipitate. Theprecipitate was collected by filtration and washed with water. Theresulting solid was dried to give an off white solid (49.10 g).

Stage 1c Preparation of

2-Naphthylamine-4,6,8-trisulfonic acid (21.87 g; 0.03 mol) was dissolvedin water (200 ml) at pH 7 whilst stirring. A solution of the product ofstage 1b (10.599; 0.03 mol) in acetone (200 ml) was added dropwise tothe naphthylamine solution at 10-13° C. over 5 minutes maintaining thepH at 7-8 by the addition of 1M aqueous sodium carbonate solution. Thisformed a reaction mixture. After stirring overnight the reaction mixturewas filtered and the filtrate was evaporated to a reduced volume. Theresulting viscous filtrate was diluted with methylated spirits 74OP andstirred for 1 hour to cause precipitation of the product. The productwas collected by filtration and washed with methylated spirits 74OP. Theproduct was dried to give a pale yellow solid (28.7 g).

Stage 1d Preparation of

The product of stage 1c (28 g) was stirred in 1M HC1(110 ml) and heatedat 80° C. for 2.5 hours. This formed a solution. The solution was thencooled to room temperature, diluted with methylated spirits 74OP (500ml) and stirred for 30 minutes. This caused the product to precipitate.The precipitate was collected by filtration and washed with methylatedspirits 74OP. The resulting solid was oven dried to give a fawn colouredsolid (13.88 g).

Stage 1e Preparation of

The intermediate of Stage 1e was prepared as described in U.S. Pat. No.7,083,670 at column 23.

Stage 1f Preparation of

The product of stage 1d (0.02 mol) was dissolved in water (200 ml) withstirring and concentrated hydrochloric acid (8 ml) was added. 1.0Msodium nitrite (21 ml; 0.021 mol) was then added drop-wise at 0-10° C.over 5 minutes to the solution containing the product of stage 1d. Afterstirring for 1 hour at 0-10° C. the excess nitrous acid was destroyed bythe addition of sulfamic acid. The resulting solution was then addeddropwise over 5 minutes to a stirred solution of the product of stage 1e(0.020 mol) in methanol (400 ml) at a temperature of less than 20° C.This formed a reaction mixture. The reaction mixture was stirredovernight at a temperature of around 25° C. The product was thenprecipitated by adding a 15% aqueous lithium chloride solution. Theprecipitate was collected by filtration and washed with 20% aqueouslithium chloride solution. The resulting precipitate was dried in anoven to give a reddish black solid 30.1 g.

Stage 1g Preparation of the Title Compound

The product of stage 1f (0.01 mol) and a pyridine coupler (0.011 mol),(prepared as described in EP 1553147 and JP-A-2003-306623) were combinedin water at 45° C. and pH 4. Isoamyl nitrite (2.69 ml:0.02 mol) was thenadded. The resultant mixture was stirred for 2.5 hours at 45° C., andthen filtered. The filtrate was adjusted to pH 7 and the product wasprecipitated by adding a 35% aqueous lithium chloride solution. Theprecipitate was then stirred with propan-1-ol (500 ml) and propan-2-ol(1000 ml) and warmed to around 60° C. to form a mixture. The mixture wasallowed to cool to a temperature of around 25° C. and the resultingsolid was collected by filtration. The solid was dissolved in water (300ml) at pH 9 and dialysed using Visking™ tubing to a conductivity of lessthan 30 μScm⁻¹. The dialysed solution was then filtered (GF/F, 0.45 μmnylon) and dried in an oven to give a reddish black solid 0.71 g. Thecompound of Example 1 had a lambda max in water of 603 nm and anextinction coefficient of 32,800 dm³ mol⁻¹ cm⁻¹.

EXAMPLE 2 Preparation of the Lithium Salt of

The compound of Example 2 was prepared in exactly the same way as inExample 1 except that the intermediate of stage 1e was replaced with

(0.020 mol) which was purchased from Alfa. The compound of Example 2 hada lambda max in water of 594 nm and an extinction coefficient of 38,900dm³ cm⁻¹.

EXAMPLE 3 Preparation of the Lithium Salt of

Prepared as in Example 1 except that:

-   -   i) In stage 1a 7-amino-1,3-disulfonaphthylene (0.5 mol) was used        in place of 2-naphthylamine-6-sulfonic acid to give the        following intermediate:

-   -   ii) In stage 1b the reaction mixture was heated to a temperature        of 50 to 70° C. for 5 hours.    -   iii) In stage 1c 2-naphthylamine-4,8-disulfonic acid (0.06 mol)        was used in place of 2-naphthylamine-4,6,8-trisulfonic acid        (0.03 mol). The compound of Example 3 had a lambda max in water        of 605 nm and an extinction coefficient of 28,700 dm³ mol⁻¹        cm⁻¹.

Comparative Dye

The comparative dye was the lithium salt of Example D 41 in U.S. Pat.No. 7,192,475:

Preparation of Inks

Inks were prepared by dissolving 3 parts by weight of the dye of Example2 and the Comparative Dye in 97 parts by weight of a liquid mediumcomprising % by weight:

Diethylene glycol 7% Ethylene glycol 7% 2-Pyrollidone 7% Surfynol ™ 4651% Tris buffer 0.2%  Water 77.8%  and adjusting the pH of the ink to 8-8.5 using aqueous sodium hydroxidesolution.

Surfynol™ 465 is a surfactant from Air Products.

Tris buffer comprises tris(hydroxymethyl)aminomethane.

The inks were prepared and referenced according to Tablet

TABLE 1 Example dye Ink Example Example 2 Ink 1 Comparative dye C. Ink 1

Ink-Jet Printing

The Inks prepared as described above were filtered through a 0.45 micronnylon filter and then incorporated into empty print cartridges using asyringe.

The inks were each ink jet printed on to Canon Professional Photo Paper(PR101) and HP Advanced Photo Paper (HP APP).

Print Testing

The light fastness of the printed ink to was measured by the differencein the reflectance optical density (ROD) before and after exposure tolight.

Each printed image was exposed to light in an Atlas™ Ci5000Weatherometer for 100 hours.

Reflectance optical density measurements were performed using a Gretag™spectrolino spectrophotometer set to the following parameters:

Measuring Geometry 0°/45° Spectral Range 380-730 nm Spectral Interval 10nm Illuminant D65 Observer 2° (CIE 1931) Density Ansi A External FillerNone

The light fastness was quantified by the percentage change in thereflectance optical density of the print, where a lower figure indicateshigher light fastness and less fade. The degree of fade is expressed asΔE where a lower figure indicates higher light fastness. ΔE is definedas the overall change in the CIE colour co-ordinates L, a, b of theprint and is expressed by the equation ΔE=(ΔL²+Δa²+Δb²)^(0.5).

Results

The results of the light fastness tests were as tabulated in Table 2.

TABLE 2 PR101 LF HP APP LF % change in % change in Ink Compound (ΔE) ROD(ΔE) ROD Ink 1 Example 2 6 12 4 9 C. Ink 1 Comparative Dye 10 19 6 10

From Table 2 it can be seen that Ink 1, containing the compound ofExample 2 has better light fastness than the comparative dye on bothpapers.

Further Compounds

Using synthetic methods analogous to those described for the previousexamples the compounds of Examples 4 to 9 were also prepared. The actualexperimentally determined lambda max values were as indicated.

EXAMPLE 4

EXAMPLE 5

EXAMPLE 6

Example 7

EXAMPLE 8

EXAMPLE 9

Further Inks

The inks described in Tables A and B may be prepared using the Compoundsdescribed in the above Examples 1 to 3. Numbers quoted refer to thenumber of parts of the relevant ingredient and all parts are by weight.The inks may be applied to paper by ink-jet printing.

The following abbreviations are used in Tables A and B:

PG=propylene glycol

DEG=diethylene glycol

NMP=N-methylpyrollidone

DMK=dimethylketone

IPA=isopropanol

MeOH=methanol

2P=2-pyrollidone

MIBK=methylisobutyl ketone

P12=propane-1,2-diol

BDL=butane-2,3-diol

CET=cetyl ammonium bromide

PHO=Na₂HPO₄

TBT=tertiary butanol

TDG=thiodiglycol

TABLE A Dye Na Example Content Water PG DEG NMP DMK NaOH Stearate IPAMEOH 2P MIBK 1 2.0 80 5 6 4 5 1 3.0 90 5 5 0.2 1 10.0 85 3 3 3 5 1 1 2.191 8 1 1 3.1 86 5 0.2 4 5 1 1.1 81 9 0.5 0.5 9 1 2.5 60 4 15 3 3 6 10 54 2 5 65 20 10 2 2.4 75 5 4 5 6 5 2 4.1 80 3 5 2 10 0.3 2 3.2 65 5 4 6 54 6 5 2 5.1 96 4 2 10.8 90 5 5 3 10.0 80 2 6 2 5 1 4 3 1.8 80 5 15 3 2.684 11 5 3 3.3 80 2 10 2 6 3 12.0 90 7 0.3 3 3 5.4 69 2 20 2 1 3 3 3 6.091 4 5

TABLE B Dye Example Content Water PG DEG NMP CET TBT TDG BDL PHO 2P PI21 3.0 80 15 0.2 5 1 9.0 90 5 1.2 5 1 1.5 85 5 5 0.15 5.0 0.2 1 2.5 90 64 0.12 1 3.1 82 4 8 0.3 6 1 0.9 85 10 5 0.2 1 8.0 90 5 5 0.3 2 4.0 70 104 1 4 11 2 2.2 75 4 10 3 2 6 2 10.0 91 6 3 2 9.0 76 9 7 3.0 0.95 5 2 5.078 5 11 6 2 5.4 86 7 7 3 2.1 70 5 5 5 0.1 0.2 0.1 5 0.1 5 3 2.0 90 10 32 88 10 3 5 78 5 12 5 3 8 70 2 8 15 5 3 10 80 8 12 3 10 80 10

1. A compound of Formula (1) or a salt thereof:

wherein: X is N or C(CN); Z is optionally substituted naphthyl; Ar is anaryl group carrying at least one substituent selected from the groupconsisting of an acetyl group, an acetate ester group, an amide group, asulfonamide group, a sulfoxide group, a sulfone group, a phosphonategroup, a nitrile group, an isonitrile group, a quaternary amine, acarbonyl group (other than a carboxylic acid), a polyhaloalkyl group ora halogen atom; and Ar may optionally be substituted with one or morefurther substituents.
 2. A compound of Formula (1) or a salt thereof asclaimed in claim 1 wherein Z is unsubstituted naphthyl.
 3. A compound ofFormula (1) or a salt thereof as claimed in claim 1 wherein Ar isnaphthyl.
 4. A compound of Formula (1) or a salt thereof as claimed inclaim 1 wherein: (i) Ar has no further substituents; or (ii) Ar has oneor more further substituents which are selected from: optionallysubstituted alkyl; optionally substituted alkoxy, optionally substitutedaryl, optionally substituted aryloxy, optionally substitutedheterocyclyl, polyalkylene oxide, sulfonic acid, carboxylic acid,hydroxy and nitro groups.
 5. A compound of Formula (1) or a salt thereofas claimed in claim 1 in which the group represented by Ar issubstituted with one or more further substituents selected fromcarboxylic acid and sulfonic acid groups.
 6. A compound of Formula (1)or a salt thereof as claimed in claim 1 wherein at least one of thecompulsory substituents on Ar is selected from —CN, —SO₂R¹ and —SO₂NR²R³wherein R¹ is optionally substituted alkyl, optionally substituted arylor optionally substituted heterocyclyl and R² and R³ are independentlyH, optionally substituted alkyl, optionally substituted aryl oroptionally substituted heterocyclyl.
 7. A compound of Formula (1) or asalt thereof as claimed in claim 6 wherein at least one of thecompulsory substituent group on Ar is —SO₂NR²R³.
 8. A compound ofFormula (1) or a salt thereof as claimed in claim 7 wherein one of R²and R³ is H and the other is: i) phenyl carrying at least one groupselected from carboxy and sulfo groups; or ii) or naphthyl carrying atleast one group selected from carboxy and sulfo groups.
 9. A compound ofFormula (1) or a salt thereof as claimed in claim 1 which is of theFormulae (2) to (4) or a salt thereof:


10. A compound of Formula (1) or a salt thereof as claimed in claim 1which is in the form of a lithium salt.
 11. A composition comprising acompound of Formula (1) or a salt thereof, as claimed in claim 1, and aliquid medium.
 12. A composition claimed in claim 11 which is an inksuitable for use in an ink-jet printer.
 13. A process for forming animage on a substrate comprising ink jet printing an ink jet printer inkas claimed in claim 12 to the substrate.
 14. A material printed with acompound of Formula (1) or a salt thereof, as claimed in claim
 1. 15. Anink-jet printer cartridge comprising a chamber and an ink jet printerink as claimed in claim 12, wherein the ink is in the chamber.
 16. Amaterial printed with a composition of claim
 11. 17. A material printedby means of a process as claimed in claim 13.